By the time the signal gets to the cell the 3 phases combine to form one signal, 1 phase. (Rotary VIC)
This signal would have 3x the frequency of each phase.
This signal would have a minimum voltage of maybe 1/3 peak voltage, and never reach zero!
For a single phase power supply you would have your voltage go from zero to peak, and Dynodon and Webmug are doing this, except their voltage is crossing zero.... this is the only thing stopping them from cracking the water in a resonant water fuel cell.